tests: factor external procedures out for portability Fortunately, "&&" is treated as "execute next, if previous doesn't fail" both on POSIX and Windows. But keeping portability of "dirstaterace.command" manually is troublesome. This patch factors external procedures out as a shell script for portability. "sh SCRIPT" always allows scripting in POSIX style. This change is also for convenience. Fixed script name can reduce command line arguments. "r" prefix is needed for "sh '$TESTTMP/dirstaterace.sh'", because $TESTTMP contains backslash on Windows.